Investigations into the mechanism of action of nitrobenzene as a mild dehydrogenating agent under acid-catalysed conditions

Protonated nitrobenzene can be used to dehydrogenate a range of hydrocarbons, which already possess at least one double bond. Kinetic and spectroscopic results, together with known electrode potentials, yield approximate limits within which protonated nitrobenzenes can be expected to effect dehydrogenation of hydroaromatic compounds. A high yielding synthesis of benzo[ j ]fluoranthene is described

Thermal evolution of biochar and its physicochemical properties during hydrothermal gasification

Biochar is a recalcitrant carbonaceous material obtained from pyrolysis and gasification of biomass and other biogenic wastes. Some of the promising biochar applications to be discussed in this presentation includes char gasification and combustion for energy production, soil remediation, carbon sequestration, catalysis, and development of activated carbon and specialty materials with biomedical and industrial uses. Several factors such as pyrolysis/gasification temperature, heating rates and residence time are the limiting factors that determine the biochar properties such as fixed carbon, volatile matter, mineral matter, surface area, porosity and pore size distribution, alkalinity, electrical conductivity, cation-exchange capacity, etc. This paper will comprehensively review the evolution of biochar from several lignocellulosic biomasses influenced by gasification temperature and residence time. Please click on the file below for full content of the abstract

Tar production in coal pyrolysis - the effect of catalysts, pressure and extraction

Imperial Users onl

Aspects of radical cation chemistry and possible applications to coal model compound reactions.

The following manuscript is a description of our efforts over the last five years to investigate and elucidate the chemical parameters and mechanisms that lead to the C-C bond cleavage reactions in organic compounds. Motivation to perform this work was provided by the reactions of certain coal model compounds under coal liquefaction conditions. These coal model compounds were found to cleave the bond connecting the naphthalene ring to the remainder of the molecule and the reactivity was attributed to be due to radical cation behavior. This behavior was different than the reactivity of radical cations of similar phenyl-containing compounds. Our contribution to this field involves the investigation of the C-C bond cleavage reactions of the radical cations of naphthyl-containing compounds. Chapter I illustrates the generation of the radical cations of naphthyl-containing compounds in solution and gas phase and their bond cleavage reactions. Their reactivity was compared to the corresponding reactivity under catalytic conditions. Chapter II examines the general oxidation reactions of the above-mentioned compounds. The purpose was to investigate the effects of counterion on the reactions. The remainder of this chapter is devoted to the investigations of the dehydrogenation reactions of related compounds. There has been interest recently in the development of new and milder dehydrogenating reagents. Three Fe compounds were found to produce the desired dehydrogenation reactivity at relatively low temperatures (130{dollar}\\sp\\circ{lcub}\\rm C{rcub}).{dollar} The final chapter of this manuscript discusses the results and conclusions derived from the sensitized irradiation of a series of esters by a triphenylpyrylium salt and oxygen. These esters were found to undergo C-C bond cleavage reactions and these reactions were found to arise by a oxygen-induced radical chain autoxidation reaction and not by radical cationic behavior as has been proposed in the literature. It is my hope that future work will be devoted to further our understanding of the general oxidations and dehydrogenations of some substrates by Fe compounds. What role does the C10{dollar}\\sb4\\sp{lcub}-{rcub}{dollar} play in these reactions? Is a radical cation intermediate involved here? These are only a few of the potential avenues that can be examined by using this manuscript as a guide. I am sure that there are more unexpected and exciting reactions waiting to be observed in the systems such as those described in this text

Effects of Lewis Acid Catalysts on the Hydrogenation and Cracking of Two-Ring Aromatic and Hydroaromatic Structures Related to Coal

An investigation was carried out of the hydrogenation and cracking of two-ring aromatic and hydroaromatic compounds catalyzed by ZnCl{sub 2} and AlCl{sub 3}. The rates of both processes are strongly affected by the Bronsted acidity of the active catalyst [e.g., H{sup +}(MX{sub n}Y){sup -}] and the Bronsted basicity of the aromatic portions of the reactant, the latter characteristic being enhanced by either methyl or hydroxyl substitution. The source of hydrogen used for hydrogenation depends on the choice of catalyst. In the presence of AlCl{sub 3}, Scholl condensation of aromatic nuclei serves as the principle source of hydrogen. Molecular hydrogen is used exclusively, though, when hydrogenation is catalyzed by ZnCl{sub 2}. The formation of reaction products and the trends in reactant reactivity are discussed on the basis of carbonium ion mechanisms